Moving Picture Experts Group-Dynamic Adaptive Streaming over HTTP (hereinafter, referred to as “DASH”) (MPEG-DASH) using the same HTTP as browsing of a web site as an internationally standardized moving image delivery protocol available for moving image delivery via the Internet has been known (for example, see Non-Patent Literature 1).
DASH implements adaptive streaming technology. In other words, a content supply side is content of the same subject, and an image quality, an angle of view size, or the like changes according to a communication environment of the Internet serving as a delivery path or a capability or a state of a reception side. A plurality of streams that differ in bit rate are prepared. On the other hand, the reception side can select an optimal stream among the plurality of streams prepared by the supply side according to the communication environment of the Internet, the decoding capability of the reception side, or the like and acquire and reproduce the selected optimal stream.
As described above, in DASH, a metafile called a media presentation description (MPD) is supplied from the supply side to the reception side so that the reception side can adaptively select, receive, and reproduce a stream.
An address (url information) of a supply source of streaming data (media data such as audio/video/subtitle) of content divided into chunks is described in the MPD. The reception side can access a server serving as a content supply source based on the url information of the MPD, requests streaming data, and receives and reproduce streaming data HTTP-delivered according to the request.
FIG. 1 illustrates an example of a configuration of a content supply system that delivers content in a streaming manner based on the DASH.
A content supply system 10 includes a plurality of content supply devices 20 (in this case, 20A, 20B, and 20C) of a side at which content is supplied and a plurality of DASH clients 30 of a side at which content is received.
The content supply device 20A delivers content of the same subject through a plurality of streams having different bit rates as a channel A. Similarly, the content supply device 20B delivers content of the same subject different from content of the channel A through a plurality of streams having different bit rates as a channel B. The same applies to the content supply device 20C. Hereinafter, when it is unnecessary to distinguish the content supply devices 20A, 20B, and 20C individually, the content supply device is referred to simply as a “content supply device 20.
The content supply device 20 includes a content management server 21, a DASH segment streamer 22, and a DASH MPD server 23.
The content management server 21 manages source data of content to be supplied to the DASH client 30, generates a plurality of pieces of streaming data having different bit rates as content of the same subject, and outputs the generated streaming data to the DASH segment streamer 22. The DASH segment streamer 22 generates a segment stream by temporally dividing each piece of streaming data into segments, and holds the segment stream as a file. The DASH segment streamer 22, as a HTTP server, HTTP-delivers the held file of the segment stream to the supply source in response to a request from the DASH client 30. The DASH segment streamer 22 notifies the DASH MPD server 23 of an address of the supply source of the file of the segment stream.
The DASH MPD server 23 generates an MPD in which, for example, the address indicating the supply source of the file of the segment stream is described, and HTTP-delivers the MPD in response to the request from the DASH client 30 of the reception side.
The DASH client 30 is connected to the content supply device 20 via the Internet 11, requests the DASH MPD server 23 to transmit the MPD, and acquires the MPD that is HTTP-delivered. The DASH client 30 requests the DASH segment streamer 22 to transmit the streaming data based on the MPD, and receives and reproduces the file that is HTTP-delivered in response to the request.
A cache server (not illustrated) that can replace the DASH MPD server 23 or the DASH segment streamer 22 is also provided on the Internet 11.